scsi: hisi_sas: send primitive NOTIFY to SSP situation only

Send primitive NOTIFY to SSP situation only, or it causes underflow issue
when sending IO. Also rename hisi_sas_hw.sl_notify() to hisi_sas_hw.
sl_notify_ssp().

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>